Investigation Of Variable Speed Constant Frequency Control Technology For Brushless Doubly Fed Wind Power Generator

Variable speed constant frequency (VSCF) wind power system is a highly efficient energy conversion system for wind power and electric energy,and is widely applied in large and medium wind generation units. Brushless doubly-fed generator (BDFG) is a new type of wind generator, which is especially fit for wind power generator. Investigation of VSCF control technology for BDFG has significant theoretical and practical values for brushless doubly-fed mchine to expand and apply in wind power field.The research subject is part of project supported by Liaoning education department foundation(20142201) which is new type brushless doubly-fed wind power generator and VSCF control technology.Because of particularity of structure of BDFG, the traditional analysis method is not applicable. Based on electromagnetic relation and electromechanical energy conversion principle of BDFG, the mathematical model of control winding rotary coordinate system for BDFG is studied. It makes a foundation for investigation of control method which is suitable for BDFG.A vector control method of BDFG is studied, which decouples active power and reactive power of power winding by controlling current of control winding. The reference power of following control system of the largest wind power is calculated, the simulation model of VSCF control system for BDFG is built and simulation study is carried out in subsynchronous state. The simulation result verifies the validity of model of BDFG and efficiency of vector control strategy based on flux linkage orientation of power winding.The excitation control system of BDFG is built based on DSP controller. Design of converter main circuit, drive circuit, protection circuit, output filter circuit, analog detection and conditioning circuit are achieved. Algorithm of modular program is studied, and design of software of VSCF control system based on vector control strategy is done preliminarily. Using variable frequency control system of asynchronous motor for simulating wind turbine, the experiment of VSCF control with independent resistance load for BDFG is carried out. The result of experiment verifies the correctness of vector control strategy and the validity of VSCF control of BDFG.